Traditionally, AC power from a commercial utility has been used as a primary source of electrical power. Telecommunications power systems have included backup power arrangements which attempt to ensure continued power in the event of black-outs and other disturbances in the commercial power grid. To accomplish this, a diesel generator is often used as a backup power source and is backed up by an array of valve-regulated lead-acid (VRLA) batteries.
These conventional systems, however, have their limitations. For one, they are dependant on commercial electrical power and thus, cannot be used in remote locations which do not have access to the AC power grid. This limitation has left much of the globe without telecommunications services.
The diesel generators used have also created problems. This is because they are noisy and emit harmful exhausts, e.g., carbon monoxide. These operational characteristics preclude their use indoors and make it undesirable to locate the diesel generator near occupied areas.
The VRLA batteries incorporated into the conventional systems have also proved to be problematic. First of all, they require considerable space. Additionally, they produce harmful and corrosive gases and, thus, require ventilation. Further, they are difficult to dispose of because of environmental problems. And they also have a short life spans and must be replaced every few years. Finally, they are not suitable for extremely hot or cold environments, thus, they must be kept in climate-controlled environments.